power electronics conference 5th december 2017 dr.-ing...

Thermal Management ofGaN Power Semiconductorsin SMD Package

Power Electronics Conference5th December 2017Dr.-Ing. Marvin Tannhäuser, Siemens AG

© Siemens AG 2017

© Siemens AG 2017 Dr.-Ing. M. Tannhäuser / CT REE SDI

GaN power semiconductors in the news as …G A M E C H A N G E R ?

Why there are not more products withGaN semiconductors on the market?

… I have no doubt that GaN will takeover the power transistor business,over the next decade…

2014, A.Lidow [2]

…switching speed, small size, competitive costand high reliability give the GaN transistorthe positive trajectory to broadly displacethe silicon MOSFET in power conversionapplications. 2017, K.Chen et all [1]

“GaN delivers total cost on par with siliconat nearly double power density.” 2017, A.Bahai [3]


What are major challenges usingGaN power semiconductors?

… from Power Electronics System view


1

In power electronics you have tomaster a wide range of different disciplines

XY

µC

Power Semiconductorƒ power moduleƒ discrete deviceƒ thermal design

V

Electronic Designƒ gate driverƒ measurement designƒ auxiliary electronics

Power ElectronicsSystem Controlƒ power circuit controlƒ embedded controller

Power Inductorƒ core and winding designƒ thermal design

EMC Managementƒ handle EMC emissionƒ avoid parasitic elements

Thermal Designƒ passive/active coolingƒ mechanical design

PowerElectronics

System

© Siemens AG 2017


1

New challenges came up infast switching power electronics

XY

µC

Power Semiconductorƒ low stray inductance in gate-and power-circuitƒ control switching speed

V

Electronic Designƒ higher dV/dt andEMC immunityƒ faster measurement

Power ElectronicsSystem Controlƒ handle low damped systemsƒ fast control algorithm

Power Inductorƒ high frequency designƒ handle fringing effect

EMC Managementƒ higher EMC emissionƒ reduce parasiticcapacitance andinductances

Thermal Designƒ cooling concepts forSMD packagesƒ handle capacitivecoupling

Power Electronicswith fast switching

GaN

© Siemens AG 2017


SMD package and thermal management

discreteTO packages

discreteSMD package

Why do we need power semiconductors in SMDpackages?

ƒ lower stray inductance in the power circuitƒ better control of the gate voltageƒ easy and full automated manufacturing

RPCB,v1: Local thermal resistance from device pad vertical trough PCB to TIMRPCB,v2: Distributed vertical thermal resistance trough PCBRPCB,sp: Spreading resistance within the copper layers of the PCBRPCB-A: Convection resistance from the PCB surface to ambient

Thermal equivalent circuit of the PCB

How can we influence/optimize the thermalmanagement of SMD power semiconductoron a standard PCB?


Analyzing the thermal PCB design –Example definition

Analyzing passive cooling and a variationof the PCB parameters

PCB parameters Value Symbol[Unit]

Given (fix) design parametersPCB size 50x50 AB [mm²]PCB substrate material FR4 -Amount of layers 4 n [-]VIA diameter 0.70 dV [mm]PAD size 8x8 APAD [mm²]

Parameters to be analyzedPCB thickness {1, 2, 3} dB [mm]Copper thickness {35, 70, 105} dC [λm]VIA plating thickness {20, 30, 40} dP [λm]

Simulation parametersAmbient temperature 25 TA [°C]

Power losses 4 Ploss [W]

PCB orientation vertical -


Analyzing the thermal PCB design –Thermal spreading within the PCB

Setup Iƒ with local thermal VIAsƒ without thermal spreading

Rth,PAD-HS

Designguide

5.8 K/W100 %

3.4 K/W59 %

3.5 K/W60 %

35 µm

Amount of local thermalVIAs should be chosen byconsidering the wholethermal resistance

With the combination of local VIAsand thermal spreading a goodperformance can be reached witha standard PCB

Setup IIƒ without local thermal VIAsƒ with thermal spreading

4.8 K/W83 %

8.2 K/W141 %

Temperature [°C]

Copper layers(4 layers)

70 µm 105 µm35 µm 70 µm

Setup IIIƒ with local thermal VIAsƒ with thermal spreading

Thermal spreading is important toreach good thermal properties. Thecopper thickness has a majorinfluence

from device padto heat sink


Analyzing the thermal PCB design –Variation of cooling method

Setup Iƒ without fanƒ without heat sink

Setup IIƒ without fanƒ with heat sink

Setup IIIƒ with fanƒ without heat sink

Setup IVƒ with fanƒ with heat sink

Power lossesat ΧT = 60 K

Rth,PAD-A

Properties/Application

17.5 K/W100 %

8.93 K/W51 %

12.4 K/W71 %

4.63 K/W26 %

3.43 W 4.84 W 6.72 W 13.0 W

ƒ passive coolingƒ small size and low weightƒ easy manufacturingƒ cheap

ƒ passive coolingƒ sealed housing/enclosure

ƒ small size and low weightƒ easy manufacturingƒ cheap

ƒmaximum power lossesƒ higher cost

Temperature [°C]

from device padto ambient


Analyzing the thermal PCB design –How to influence the thermal performance?

Thermal spreading within the PCB is as important as the use of local thermal VIAsƒ the thickness has a major influence to the PCB spreading resistanceƒ a good thermal spreading decreases the negative influence of a TIM and the board thicknessƒ less local VIAs allow a degree of freedom for the electrical design of the power cellƒ a thermal PCB resistance of 3 to 4 K/W can be reached with a standard PCB with passive cooling

The relevance of the thermal PCB design depends on the cooling method and applicationApplication with low power lossesƒ passive cooling without heat sink and fan is possibleƒ easy and high volume manufacturing can be achievedƒ low cost for manufacturing and maintenanceApplication with high power lossesƒ a fan and heat sink is needed

An optimal thermal PCB design needs in any case further investigations and calculationsThe paper shows examples to understand the possibilities and limits of the thermal PCB design


GaN converter prototype with a thermal managementonly by the PCB design

Converter prototype with GaN SMD power semiconductors demonstrates a passive coolingwithout heat sink and fan


GaN converter prototypeMeasurement results (single phase)

Measurement conditionsPower: 1 kW (single phase)Switching frequency: 175 kHzCooling: Passive (no fan, no heat sink, TA = 25°C)

SMD in detail SMD temperature = 57°C

Sinusoidal output voltage Efficiency measurement


Conclusion and outlookFuture trend: Integrated Power Electronics

FUTURE“all-digital”

Integrated Power Electronics

GaN enables newPower Electronics Systemsƒ higher switching speedƒ higher efficienciesƒ smaller passive componentsƒ smaller and lighter converter systemsƒ easy and high volume manufacturingƒ lower system costƒ easy power scalingƒ higher system performanceƒ etc…

Challenges for future fast switching Integrated Power Electronicsƒ cooling concepts for SMD power semiconductorsƒ power inductors for high switching frequencyƒ auxiliary electronics (gate-driver, isolators, measurements) with high EMC-immunityƒ fast control concepts for PE systems with low dampingƒ concepts to handle high EMC emissionƒ new topologies for high switching speed and frequency

[4]


References

No. Reference

[1] Kevin J. Chen, Oliver Häberlen, Alex Lidow, Chun lin Tsai, Tetsuzo Ueda, Yasuhiro Uemoto andYifeng Wu; “GaN-on-Si Power Technology: Devices and Applications”, IEEE Transactions on ElectronDevices, Vol.64, no.3, 2017

[2] Alex Lidow, “EPC: GaN Ambition”, Comound Semiconductor, July 2014,https://compoundsemiconductor.net/article/94531-epc-gan-ambition.html

[3] Tom Keim and Ashok Bindra; „From Components to Power Systems – APEC showcases exceptionaltechnologies across the board“; IEEE Power Electronics Magazine, June 2017Ahmad Bahai; “Power semiconductor technology intelligence for tomorrow’s solutions”; IEEE Xplore,https://ieeetv.ieee.org/mobile/video/keytalk-dr-ahmad-bahai-power-semiconductor-technologyintelligence-for-tomorrows-solutions-apec-2017

[4] Robert C.N. Pilawa-Podgurski; Little Box Challenge Publication, UIUC Pilawa Group – 545-rk37Vu-57827


Contact

Siemens AGCorporate TechnologySoftware Defined Inverter – Digital Power Electronics

CT REE SDIDr.-Ing. Marvin TannhäuserSenior Key Expert

E-mail: [email protected]

Frauenauracher Straße 8091056 ErlangenGERMANY

power electronics conference 5th december 2017 dr.-ing...

Documents